1. Field of the Invention
The present invention relates to a device for sorting products, comprising bogies which are movable in a direction of transport along a conveying path, which bogies are pivotally interconnected, supporting platforms comprising a supporting surface for supporting products to be sorted, each of said supporting platforms comprising supporting elements which are movable with respect to an adjacent supporting element for changing the circumference of the supporting platform in question during passage of a bend in the conveying path, which supporting elements consist of two outer supporting elements which, seen in the direction of transport, are located at the front side and the rear side, respectively, of the supporting platform in question and at least one intermediate supporting element positioned between said outer supporting elements, supporting means for supporting the supporting platforms on the bogies, and tilting means for tilting the supporting platforms about a tilt axis that extends parallel to the direction of transport.
2. Discussion of the Background
Devices which are capable of discharging products sideways by tilting a supporting platform can be used in sorting various kinds of products, such as parcel post or pieces of luggage at airports. The above-described tilting of a supporting platform will cause a product supported on the supporting surface thereof to slide off the supporting surface under the influence of the force of gravity. Products can thus be sorted by having said tilting take place at a selected position.
A device as referred to in the introduction is described in U.S. Pat. No. 4,031,998. Said sorting device uses an endless chain, whose links can be regarded as bogies. Each link supports a leg comprising a lower leg part that is rigidly connected to the associated link and an upper leg part that is connected for lateral pivoting movement to the lower leg part. At its upper end, the upper leg part carries a slat-like supporting element that extends transversely to the direction of transport. A number of adjacent supporting elements jointly form a supporting platform. The supporting elements associated with a supporting platform partially overlap, so that lateral pivoting of an intermediate supporting elements will result in the remaining supporting elements pivoting along therewith, so that the supporting platform will pivot as a whole. Said pivoting of an intermediate supporting element is effected by vertically deflecting a cam wheel that is fixedly connected to an upper leg part.
A major advantage of the use of the slat-like supporting elements is that comparatively small relative movements between the supporting elements suffice for passing bends, while in addition the successive supporting surfaces of each supporting platform not only individually but also jointly form an at least substantially closed surface upon passing bends. In this way (parts of) products are prevented from getting wedged between adjacent supporting elements of either one supporting platform or of adjacent supporting platforms.
Besides the above advantages, the known sorting device also has major drawbacks. In the first place these are connected with the fact that the number of links is necessarily equal to the number of supporting elements. This implies that also the dimensions of the links and the supporting elements must be geared to each other. These preconditions impose significant restrictions on the designer of a sorting device as regards the design possibilities. Thus the designer will be confronted at some point with the limits of what is technically and economically feasible, given the fact that the dimensions of the supporting elements in the direction of transport must remain within bounds. After all, this would mean that it will also be necessary to use shorter links and that, in addition, a greater density of legs individually supporting the supporting elements will be required, which legs themselves will moreover need to be of increasingly smaller and more vulnerable construction.
Another important drawback is connected with the fact that a number of successive, mutually pivotable links are provided for supporting a single supporting platform. To an increasing extent, modern sorting devices are fitted with an electric motor for each supporting platform for tilting said supporting platform. Said electric motors move along with the supporting platforms. The mutually pivotable links are unsuited for attaching the electric motors thereto, however, or this is at least not easy to realise.
Partly because of the aforesaid drawbacks, designers refrain from the use of slat-like supporting elements in modern sorting devices comprising tilting supporting platforms, in spite of the above-described advantages thereof.
An example of such a modern sorting device is described in International patent application WO-A1-99/33719. More specifically, reference is made within the framework of the present invention to the second embodiment thereof, which is described with reference to FIGS. 10-13 of said International patent application. Said embodiment concerns a sorting system comprising an endless train of bogies that move in a direction of transport along a conveying path. Each bogie supports a main supporting surface comprising a product-supporting surface, whose dimensions in the direction of transport are larger than those in the direction perpendicular thereto. To prevent gaps being formed between main supporting surfaces of successive bogies, a bridging surface is provided both at the front side and at the rear side of each main supporting surface. The bridging surface at the front side of a main supporting surface can pivot with respect to a pivot axis that extends perpendicularly to the main supporting surface, and at the front side it abuts against the rear side of the supporting surface at the rear end of a next bogie. The bridging surface at the rear side of a main supporting surface is capable of limited movement against spring action in the direction of transport with respect to the main supporting surface. The front bridging surfaces ensure that no gaps are formed between main supporting surfaces of successive bogies when passing horizontal bends, whilst the rear bridging surfaces ensure that no gaps are formed between main supporting surfaces of successive bogies when passing vertical bends.
A drawback of such a prior art sorting device is the fact that because of the small number of supporting elements, being the main supporting surface and the bridging surfaces, and the dimensions thereof, the supporting elements move a relatively large distance and/or undergo a relatively large angular displacement with respect to each other during passage of a bend, as a result of which the position on a supporting platform of products present thereon may change undesirably while passing a bend. In addition to that there is a risk of gaps being formed between adjacent supporting platforms when a product finds its way between said supporting platforms and thereby forces the facing bridging surfaces of the respective supporting platforms apart.
Reference is furthermore made to European patent application EP-A2-869 086. Said patent describes a sorting device in which use is made of a train of supporting platforms, which are each capable of individual tilting movement and which each comprise two overlapping slat-like supporting elements, which can only tilt in unison. As with the sorting device according to U.S. Pat. No. 4,031,998, the number of links of the chain by which the supporting platforms are moved is related to the number of supporting elements, with all its limitations. Moreover, the possibility of individual tilting of the supporting platforms, which each have a comparatively small dimension, seen in the direction of transport, also makes the sorting device complex, costly and unsuitable for tilting the supporting platforms via (electric) motors that move along with said supporting platforms.